Influences of the bag constant on properties of hybrid stars  

作　　者：包特木尔巴根 李根全 王宗昌 杨兴强 刘广洲 

机构地区：[1]College of Physics and Electronic Engineering, Nanyang Normal University [2]College of Physics, Jilin University

出　　处：《Chinese Physics C》2011年第6期539-542,共4页中国物理C（英文版）

基　　金：Supported by the National Natural Science Foundation of China (10275029, 10675054);Natural Science Foundation of Henan Education Department (2008A140009);Science Foundation of Nanyang Normal University (nytc2006k98);Natural Science Foundation of Henan Province (112300410187)

摘　　要：Influences of the bag constant on the properties of hybrid stars are investigated by using relativistic mean field theory and the MIT bag model to describe the hadron phase and quark phase in the interior of neutron stars, respectively. Our results indicate that the onset of hadron-quark phase transition is put off and the appearance of hyperon species is increased with the increase in bag constant. As a result, the hybrid star equation of state for a mixed phase range stiffens whereas that of the quark phase range softens, and the gravitational mass as well as the corresponding radius of hybrid stars are increased obviously. The gravitational mass of a hybrid star is increased from 1.42 M （M is solar mass） to 1.63M and the corresponding radius is changed from 9.1 km to 12.2 km when the bag constant （B1/4） is increased from 170 MeV to 200 MeV. It is interesting to find that hybrid star equations of state become non-smooth when the TM2 parameter sets in the framework of relativistic mean field theory used to describe the hadronic matter, and consequently, the third family of compact stars appear in the mass-radius relations of hybrid stars in the narrow scope of the bag constant from 175 MeV to 180 MeV. These show that the choice of the bag constant in the MIT bag model has significant influence on the properties of hybrid stars.Influences of the bag constant on the properties of hybrid stars are investigated by using relativistic mean field theory and the MIT bag model to describe the hadron phase and quark phase in the interior of neutron stars, respectively. Our results indicate that the onset of hadron-quark phase transition is put off and the appearance of hyperon species is increased with the increase in bag constant. As a result, the hybrid star equation of state for a mixed phase range stiffens whereas that of the quark phase range softens, and the gravitational mass as well as the corresponding radius of hybrid stars are increased obviously. The gravitational mass of a hybrid star is increased from 1.42 M （M is solar mass） to 1.63M and the corresponding radius is changed from 9.1 km to 12.2 km when the bag constant （B1/4） is increased from 170 MeV to 200 MeV. It is interesting to find that hybrid star equations of state become non-smooth when the TM2 parameter sets in the framework of relativistic mean field theory used to describe the hadronic matter, and consequently, the third family of compact stars appear in the mass-radius relations of hybrid stars in the narrow scope of the bag constant from 175 MeV to 180 MeV. These show that the choice of the bag constant in the MIT bag model has significant influence on the properties of hybrid stars.

关 键 词：hybrid stars bag constant equations of state mass-radius relations 

分 类 号：P144[天文地球—天体物理]